Herbaceous production lost to tree encroachment in United States rangelands

Data products and modeling code supporting the publication:

Herbaceous production lost to tree encroachment in United States rangelands in the Journal of Applied Ecology.

Manuscript DOI: 10.1111/1365-2664.14288

Abstract

1. Rangelands of the United States provide ecosystem services that benefit society and rural economies. Native tree encroachment is often overlooked as a primary threat to rangelands due to the slow pace of tree cover expansion and the positive public perception of trees. Still, tree encroachment fragments these landscapes and reduces herbaceous production, thereby threatening habitat quality for grassland wildlife and the economic sustainability of animal agriculture.  
2. Recent innovations in satellite remote sensing permit the tracking of tree encroachment and the corresponding impact on herbaceous production. We analyzed tree cover change and herbaceous production across the western United States from 1990 to 2019.
3. We show that tree encroachment is widespread in U.S. rangelands; absolute tree cover has increased by 50% (77,323 km²) over 30 years, with more than 25% (684,852 km²) of U.S. rangeland area experiencing tree cover expansion. Since 1990, 302 ± 30 Tg of herbaceous biomass have been lost. Accounting for variability in livestock biomass utilization and forage value reveals that this lost production is valued at between $4.1 - $5.6 billion U.S. dollars.
4. Synthesis and applications: The magnitude of impact of tree encroachment on rangeland loss is similar to conversion to cropland, another well-known and primary mechanism of rangeland loss in the U.S. Prioritizing conservation efforts to prevent tree encroachment can bolster ecosystem and economic sustainability, particularly among privately-owned lands threatened by land-use conversion.

Description

This archive contains data products and modeling code for production loss and tree cover change estimates provided in the accompanying refereed publication. The easiest way to view and use these data is in Google Earth Engine:

• https://smorford.users.earthengine.app/view/yield-gap
• https://code.earthengine.google.com/8ad19c7f7a6e04b377953326b274f98d

Summary data products are included in the data-products folder, and include links and scripts to download all annual data discussed in the manuscript. The full dataset is roughly 660GB and cannot be achieved on Zonodo as of summer 2022.

Similarly, the model directory contains the primary codebase for processing raw tree cover data and running XGBoost modeling training and inference for the production loss model. To recreate the production loss data will require downloading approximately 900GB of biomass data and 250GB of tree cover data; total project size will be approximate 1.8 TB after inference.

Data can also be downloaded directly from the University of Montana web servers:

• http://rangeland.ntsg.umt.edu/data/rap/rap-vegetation-biomass/v2/
• http://rangeland.ntsg.umt.edu/data/rap/rap-derivatives/yield-gap/v1/

Journal citation:

Morford, S.L., Allred, B.W., Twidwell, D., Jones, M.O., Maestas, J.D., Roberts, C.P. and Naugle, D.E., Accepted. Herbaceous production lost to tree encroachment in United States rangelands. Journal of Applied Ecology, August 2022.